Liquid crystal display comprising a biaxial plate and a C-plate

ABSTRACT

A vertical alignment type liquid crystal display, which has a liquid crystal layer whose retardation value is about 600 nm or more, can solve the viewing angle problems associated with the wider viewing angle. The liquid crystal display can include a vertical alignment liquid crystal cell, and first and second polarizing plates cross-Nicol disposed on respective sides of the liquid crystal cell. The liquid crystal cell has a liquid crystal layer with a retardation of about 600 nm or more. A biaxial plate is provided between the liquid crystal cell and the first polarizing plate, and two C-plates are provided between the liquid crystal cell and the second polarizing plate.

This application claims the priority benefit under 35 U.S.C. §119 ofJapanese Patent Application No. 2006-129869 filed on May 9, 2006, whichis hereby incorporated in its entirety by reference.

BACKGROUND

1. Technical Field

The disclosed subject matter relates to a liquid crystal display of avertical alignment type. In particular, the presently disclosed subjectmatter relates to a liquid crystal display having a liquid crystal layerwith a retardation of about 600 nm or more and an effective viewingangle compensation structure therefor.

2. Description of the Related Art

In recent years, viewing angle compensation means having a variety ofoptical characteristics have been proposed for vertical alignment typeliquid crystal displays. In particular, examples of such viewing anglecompensation means include viewing angle compensation plates.

Japanese Patent Publication No. Hei 7-69536 discloses a liquid crystaldisplay having a vertical alignment type liquid crystal cell and firstand second polarizing plates which are cross-Nicol disposed onrespective sides of the liquid crystal cell. In this liquid crystaldisplay, viewing angle compensation means is provided between the liquidcrystal cell and any one of the first and second polarizing plates.

In the disclosed liquid crystal display, the viewing angle compensationmeans comprises a viewing angle compensation plate having three mainrefractive indices. In this instance, one of the main refractive indicesis smaller than the other two main refractive indices, and an axiscorresponding to the smallest main refractive index is parallel to thenormal direction of the compensation plate.

In addition to this, the patent document discloses that it is effectiveto utilize a negative uniaxial compensation plate, so-called “C-plate,”as a viewing angle compensation plate, which has an optical axis beingparallel to the normal direction of the compensation plate. Further tothis, the patent document also discloses that it is effective to utilizea biaxial compensation plate, so-called “biaxial plate,” as a viewingangle compensation plate, which is a medium having biaxial opticalanisotropy and which has a minimum main refractive index with its axisbeing parallel to the normal direction of the compensation plate.

The invention of Japanese Patent No. 3330574 includes viewing anglecompensation means which is provided between the liquid crystal cell andone polarizing plate as in the previous case. This viewing anglecompensation means utilize a viewing angle compensation plate, so-called“biaxial plate,” which has three main refractive indices where one ofthe main refractive indices is smaller than the other two mainrefractive indices, and an axis corresponding to the smallest mainrefractive index is parallel to the normal direction of the compensationplate. This biaxial plate is arranged such that larger one of the othertwo main refractive indices, namely the delay phase axis in the in-planedirection of the viewing angle compensation plate, is substantiallyparallel to or perpendicular to the absorption axis of the adjacentpolarizing plate. In this configuration, the patent document disclosesthat the retardation in an in-plane direction of 120 nm or less isadvantageous.

The invention of Japanese Patent No. 3027805 includes viewing anglecompensation means which is provided between the liquid crystal cell andone polarizing plate as in the previous cases. The viewing anglecompensation means is composed of a so-called A-plate (which has anoptical axis in an in-plane direction and is a positive uniaxialcompensation plate whose refractive index anisotropy is positive) and aso-called C-plate (which has an optical axis being parallel to thenormal direction of the compensation plate and is a negative uniaxialcompensation plate whose refractive index anisotropy is negative). Inthis viewing angle compensation means, the A-plate, the C-plate, and thepolarizing plate are arranged in this order from the liquid crystal cellside. In this instance, the patent document discloses that theretardation of the A-plate is advantageously set to 120 nm or less.

Japanese Patent Laid-Open Publication No. 2000-19518 discloses avertical alignment type liquid crystal display in which liquid crystalsare oriented in an axial symmetric manner in each of liquid crystalareas when a voltage is applied thereto. It is also disclosed that thisliquid crystal display is advantageously provided with a biaxial plateas disclosed in Japanese Patent Publication No. Hei 7-69536 or thepublication of Japanese Patent No. 3330574, or a viewing anglecompensation plate prepared by stacking the A-plate and the C-plate asdisclosed in Publication of Japanese Patent No. 3027805.

As shown, the inventions disclosed in the publications of JapanesePatent No. 3330574 and No. 3027805 and Japanese Patent Laid-OpenPublication No. 2000-19518 have proposed the respective opticalcompensation plates which are configured based on the principle of theviewing angle compensation means provided to the liquid crystal displayof vertical alignment type disclosed in Japanese Patent Publication No.Hei 7-69536 and are further improved by setting certain viewing anglecompensation conditions.

Here, Japanese Patent Publication No. Hei 7-69536 does not specificallydiscuss the product of the birefringence of the liquid crystal and thecell thickness, namely, the retardation of the liquid crystal layer. Inthis regard, the publications of Japanese Patent No. 3330574 and No.3027805 and Japanese Patent Laid-Open Publication No. 2000-19518 eachdisclose that the advantageous effect can be obtained within a certainrange of retardation values. Specifically, the publications of JapanesePatent No. 3330574 and No. 3027805 disclose that the retardation valueof the liquid crystal layer is advantageously in the range of from 80 nmto 400 nm. Japanese Patent Laid-Open Publication No. 2000-19518discloses that the retardation value of the liquid crystal layer isadvantageously in the range of from 300 nm to 550 nm.

Since the liquid crystal displays disclosed in the publications ofJapanese Patent No. 3330574 and No. 3027805 and Japanese PatentLaid-Open Publication No. 2000-19518 are active matrix type liquidcrystal displays that are typically represented by TFT-LCDs, theretardation values are specifically limited as described above. In otherwords, the above-referenced publications do not consider cases in whicha liquid crystal layer in liquid crystal display has a largerretardation value.

SUMMARY OF THE INVENTION

In view of the above-described and other problems, it is an object ofthe presently disclosed subject matter to provide a viewing anglecompensation technique that is suitable for a liquid crystal displayhaving a liquid crystal layer with a high retardation of about 600 nm ormore. The liquid crystal layer having such a high retardation value isnot addressed in vertical alignment type liquid crystal displaysdisclosed in the publications of Japanese Patent No. 3330574 and No.3027805 and Japanese Patent Laid-Open Publication No. 2000-19518. Thepresently disclosed subject matter can provide viewing anglecompensation means to obtain a significant viewing angle improvingeffect.

A viewing angle compensation plate constituting the viewing anglecompensation means can be prepared by stretching a norbornene-basedresin material. However, the existing processing technique cannotincrease the retardation in the thickness direction of the compensationplate.

The existing processing technique can manufacture biaxial plates andC-plates each having a maximum retardation value of approximately 250 nmin the thickness direction of the compensation plate when taking stablemass-production into consideration. In the case where a deterioration isallowed which is a reduction in yield within an allowable range, theexisting processing technique can provide compensation plates having amaximum retardation value of approximately 270 nm.

In view of these circumstances, the publications of Japanese Patent No.3330574 and No. 3027805 and Japanese Patent Laid-Open Publication No.2000-19518 disclose techniques in which a viewing angle compensationplate is provided on both sides of the liquid crystal cell.

It should be noted that an appropriate viewing angle compensation platetypically has approximately the same retardation value in its thicknessdirection as that of the liquid crystal layer of a liquid crystaldisplay.

When a liquid crystal display having a liquid crystal layer whoseretardation value is about 600 nm or more is provided with a viewingangle compensation plate on both sides of the liquid crystal cell foroptimum viewing angle compensation, the viewing angle compensationplates manufactured by the existing processing technique cannot providesufficient retardations in the thickness direction of the plate.

In view of this problem, it is conceivable that two or more viewingangle compensation plates are stacked to be provided on both sides ofthe liquid crystal cell in order to increase the retardation value bysumming up the respective retardation values in the thickness direction.Even if the liquid crystal display has such a configuration, when aviewer observes the liquid crystal display at viewing angles of 40degrees or more, for example, there is a problem in which lightundesirably passes through the liquid crystal display even in a normallyblack display area.

In view of the above-described circumstances, in one aspect, it is anobject of the presently disclosed subject matter to provide a verticalalignment type liquid crystal display having a liquid crystal layerwhose retardation value is 600 nm or more, the liquid crystal displaybeing provided with a high performance viewing angle compensationcomponent(s) which can achieve optimum viewing angle compensation andcan solve the viewing angle problems associated with the wider viewingangle.

One aspect of the presently disclosed subject matter is a liquid crystaldisplay which includes: a vertical alignment type liquid crystal cellhaving a liquid crystal layer containing liquid crystal molecules, aretardation of the liquid crystal layer being configured to be about 600nm or more; a first polarizing plate and a second polarizing plateprovided to respective sides of the liquid crystal cell, the first andsecond polarizing plates each having an absorption axis and beingcross-Nicol disposed, the first and second polarizing plates beingdisposed such that the respective absorption axes form a predeterminedangle with respect to a direction in which the liquid crystal moleculesare slanted by application of a voltage greater than a thresholdvoltage; a simple-matrix driving system; a biaxial plate providedbetween the liquid crystal cell and the first polarizing plate, thebiaxial plate having refractive indices nx, ny, and nz in in-planedirections and in the thickness direction, respectively, in which arelationship of nx>ny>nz is satisfied, the biaxial plate being disposedsuch that its delay phase axis in the in-plane direction isperpendicular to the absorption axis of the first polarizing plate; anda C-plate provided between the liquid crystal cell and the secondpolarizing plate, the C-plate having refractive indices nx, ny, and nzin in-plane directions and in the thickness direction, respectively, inwhich a relationship of nx=ny>nz is satisfied.

In this liquid crystal display in accordance with the above describedaspect, the biaxial plate may have an in-plane retardation of about 100nm or less.

Another aspect of the presently disclosed subject matter is a liquidcrystal display which includes: a vertical alignment type liquid crystalcell having a liquid crystal layer containing liquid crystal molecules,a retardation of the liquid crystal layer being configured to be about600 nm or more; a first polarizing plate and a second polarizing plateprovided to respective sides of the liquid crystal cell, the first andsecond polarizing plates each having an absorption axis and beingcross-Nicol disposed, the first and second polarizing plates beingdisposed such that the respective absorption axes form a predeterminedangle with respect to a direction in which the liquid crystal moleculesare slanted by application of a voltage greater than a thresholdvoltage; a simple-matrix driving system; a first C-plate and an A-plateprovided between the liquid crystal cell and the first polarizing platein this order, the A-plate having refractive indices nx, ny, and nz inin-plane directions and in the thickness direction, respectively, inwhich a relationship of nx>ny=nz is satisfied, the first C-plate havingrefractive indices nx, ny, and nz in in-plane directions and in thethickness direction, respectively, in which a relationship of nx=ny>nzis satisfied, the A-plate having its optical axis disposed such that theoptical axis is perpendicular to the absorption axis of the firstpolarizing plate; and a second C-plate provided between the liquidcrystal cell and the second polarizing plate, the second C-plate havingrefractive indices nx, ny, and nz in in-plane directions and in thethickness direction, respectively, in which a relationship of nx=ny>nzis satisfied.

In this liquid crystal display in accordance with the above describedaspect, the A-plate may have an in-plane retardation of about 100 nm orless.

In the liquid crystal display configured as described above, the C-platedisposed between the liquid crystal cell and the second polarizing platecan be formed of two or more stacked plates.

In accordance with these aspects of the presently disclosed subjectmatter, even when the liquid crystal display includes a verticalalignment type liquid crystal cell having a liquid crystal layer whoseretardation is about 600 nm or more, viewing angle compensation can beachieved with high accuracy. Furthermore, viewing angle compensation canbe achieved highly effectively and easily implemented.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics, features, and advantages of thepresently disclosed subject matter will become clear from the followingdescription with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view showing the configuration ofa liquid crystal display of a first exemplary embodiment made inaccordance with principles of the disclosed subject matter;

FIG. 2 is a simplified cross-sectional view of a liquid crystal cell ofthe liquid crystal display of the first exemplary embodiment shown inFIG. 1;

FIG. 3 is a partial enlarged cross-sectional view of the liquid crystalcell, showing the rubbing direction;

FIG. 4 is an enlarged cross-sectional view showing a display unit of theliquid crystal display of the first exemplary embodiment;

FIG. 5 includes (a) through (f) optical characteristics diagrams of aliquid crystal cell, polarizing plates, a biaxial plate, and C-plates,respectively, all of which constitute the display unit of FIG. 4;

FIG. 6 is an enlarged cross-sectional view showing a display unit of aliquid crystal display of a second exemplary embodiment;

FIG. 7 includes (a) through (e) optical characteristics diagrams of aliquid crystal cell, polarizing plates, a biaxial plate, and an opticalplate, respectively, all of which constitute the display unit of FIG. 6;

FIG. 8 is an enlarged cross-sectional view showing a display unit of aliquid crystal display of a third exemplary embodiment;

FIG. 9 includes (a) through (g) optical characteristics diagrams of aliquid crystal cell, polarizing plates, an A-plate, and a C-plate,respectively, all of which constitute the display unit of FIG. 8;

FIG. 10 is an enlarged cross-sectional view showing a display unit of aliquid crystal display of a fourth exemplary embodiment;

FIG. 11 includes (a) through (f) optical characteristics diagrams of aliquid crystal cell, polarizing plates, an A-plate, and a C-plate,respectively, all of which constitute the display unit of FIG. 10;

FIG. 12 is an enlarged cross-sectional view showing a display unit of aliquid crystal display of a reference example;

FIG. 13 includes (a) through (f) optical characteristics diagrams of aliquid crystal cell, polarizing plates, and biaxial plates,respectively, all of which constitute the display unit of FIG. 12; and

FIG. 14 is a graph showing the viewing angle characteristics of liquidcrystal displays made in accordance with the principles of the presentlydisclosed subject matter and a liquid crystal display made in accordancewith the referenced technique.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description will now be given of exemplary embodiments that areconstructed in accordance with principles of the presently disclosedsubject matter with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a liquid crystal display of afirst exemplary embodiment.

This liquid crystal display can be driven based on a simple-matrixdriving method using a duty ratio of 1/4 or more.

The liquid crystal display according to this embodiment includes aliquid crystal cell 11, polarizing plates 12 and 13 disposed onrespective sides of the liquid crystal cell 11, a biaxial plate 14disposed between the liquid crystal cell 11 and the polarizing plate 12,and two C-plates 15 and 16 disposed between the liquid crystal cell 11and the polarizing plate 13.

In addition to this, the liquid crystal display can include a backlightunit 17, a drive circuit board 18, and the like. The components can beenclosed by a resin cover 19, for example, to constitute a display unitfor the liquid crystal display.

It should be noted that hereinafter the side where the backlight unit 17is provided is a rear side and the side where the polarizing plate 12 isprovided is a front side.

FIG. 2 is a schematic cross-sectional view of the liquid crystal cell 11described above.

The liquid crystal cell 11 can include transparent substrates 22 and 23made of a glass substrate, for example, a pair of transparent electrodes20 and 21 formed thereon, and liquid crystal 24 interposed therebetween.

It should be appreciated that the drive circuit board 18, and the pairof transparent electrodes 20 and 21, and the like can constitute thesimple-matrix driving system.

Orientation films 25 and 26 are formed on the respective opposedsurfaces of the transparent electrodes 20 and 21.

It should be appreciated that the liquid crystal cell 11 is configuredas a vertical alignment type liquid crystal cell in the presentexemplary embodiment. The orientation films 25 and 26 can be preparedusing a vertical alignment film SE-1211 manufactured by Nissan ChemicalIndustries, Ltd., and by rubbing the film in the arrow direction of FIG.3 by means of rayon rubbing cloth in order to impart a pre-tilt angle tothe liquid crystal 24 molecules.

The transparent substrates 22 and 23 can be overlapped with each othervia not-shown gap control materials with a diameter of 5 μm. Liquidcrystal manufactured by Merck Ltd. can be used as the liquid crystal 24,which has a birefringence Δn of 0.16 and negative dielectric anisotropy(when applying a voltage, the liquid crystal molecules are slanted froma vertical direction).

Therefore, the liquid crystal layer configured in this example has aretardation of 800 nm.

The liquid crystal 24 can be sealed within the gap between thetransparent substrates 22 and 23 by adhering a sealing material 27around the transparent electrodes 20 and 21.

FIG. 4 shows a cross-sectional view of the display unit including theliquid crystal cell 11, the polarizing plates 12 and 13, the biaxialplate 14, and the C-plates 15 and 16. As shown in the drawing, thepolarizing plate 12 is attached to the front side of the liquid crystalcell 11 with the biaxial plate 14 interposed therebetween. Thepolarizing plate 13 is attached to the rear side of the liquid crystalcell 11 with the two C-plates 15 and 16 interposed therebetween.

The polarizing plates 12 and 13 are cross-Nicol disposed as an uppermostlayer and an undermost layer of the display unit such that theirabsorption axes each forms 45 degrees with the direction in which theliquid crystal molecules are slanted by rubbing.

In this instance, the term “cross-Nicol” shall mean that the absorptionaxes of the polarizing plates 12 and 13 cross at 90 degrees. It shouldbe appreciated, however, that the term “cross-Nicol” includes the casewhere they cross at approximately 90 degrees ±several degrees dependingon actual adjustments.

In the present exemplary embodiment, the biaxial plate 14 can be a phasedifference plate having characteristics in which refractive indices nx,ny, and nz of the biaxial plate in in-plane directions and in thethickness direction, respectively, satisfy a relationship of nx>ny>nz.For example, this biaxial plate 14 may have a retardation in thein-plane directions of 50 nm and a retardation in the thicknessdirection of 240 nm, and is disposed such that its delay phase axis inthe in-plane direction is perpendicular to the absorption axis of theadjacent polarizing plate 12 at the front side.

In the present exemplary embodiment, the C-plates 15 and 16 each can bea phase difference plate having characteristics in which refractiveindices nx, ny, and nz of the C-plate in in-plane directions and in thethickness direction, respectively, satisfy a relationship of nx=ny>nz.The C-plates 15 and 16 each have a retardation of 220 nm and are stackedtogether.

FIG. 5 includes (a) through (f) optical characteristics diagrams of theliquid crystal cell 11, the polarizing plates 12 and 13, the biaxialplate 14, and the C-plates 15 and 16, respectively. FIG. 5( a) shows theabsorption axis 12 a of the front side polarizing plate 12, FIG. 5( b)shows the delay phase axis 14 a in the in-plane direction of the biaxialplate 14, and FIG. 5( c) shows rubbing directions performed on theliquid crystal cell 11, specifically, in which a dotted arrow 11 a isthe rubbing direction performed on the front side substrate, and a solidarrow 11 b is the rubbing direction performed on the rear sidesubstrate. In addition to this, FIGS. 5( d) and 5(e) show the opticalaxes 15 a and 16 a of the respective C-plates 15 and 16, respectively(note that the optical axes are in the normal direction with respect tothe surface), and FIG. 5( f) shows the absorption axis 13 a of the rearside polarizing plate 13.

A description will now be given of a second exemplary embodiment. FIG. 6shows a cross-sectional view of a display unit of the second exemplaryembodiment. FIG. 7 shows the optical characteristics diagrams of aliquid crystal cell 11, polarizing plates 12 and 13, a biaxial plate 14,and an optical plate 38, respectively.

In the second exemplary embodiment the C-plates of the first exemplaryembodiment are replaced with an optical plate 38. The optical plate 38is disposed between the liquid crystal cell 11 and the rear sidepolarizing plate 13. The optical plate 38 can be composed of acholesteric liquid crystal polymer having a twisted pitch shorter thanthe wavelength of visible light.

It is known that the optical plate 38 having the above describedconfiguration has the similar optical function to the C-plate.Therefore, the birefringence of cholesteric liquid crystal and thethickness of the liquid crystal layer can be controlled to provide aplate having a large retardation, which cannot be achieved by the priorart technique in which, for example, a norbornene-based resin materialis stretched.

In the present exemplary embodiment, the optical plate 38 is composed ofthe cholesteric liquid crystal polymer having a retardation of 440 nm,which is equal to the sum of the retardations of two C-plates used inthe first exemplary embodiment. This configuration can provide the sameor substantially same effects as that of the first exemplary embodimentin terms of its optical properties.

It should be noted that as shown in FIG. 7( d) the optical axis 38 a ofthe optical plate 38 is in the normal direction with respect to thesurface.

A description will now be given of a third exemplary embodiment. FIG. 8shows a cross-sectional view of a display unit of the third exemplaryembodiment.

The present exemplary embodiment is the same as the first exemplaryembodiment except that the biaxial plate is replaced with an A-plate 39and a C-plate 40 between the liquid crystal cell 11 and the front sidepolarizing plate 12.

In the present exemplary embodiment, the A-plate 39 can be a phasedifference plate having characteristics in which refractive indices nx,ny, and nz of the A-plate in in-plane directions and in the thicknessdirection, respectively, satisfy a relationship of nx>ny=nz. In thisexample, this A-plate 39 has a retardation of 70 nm.

In addition to this, the C-plate 40 has a retardation of 200 nm.

Accordingly, this configuration can provide the same or substantiallysame effects as that of the first exemplary embodiment in terms of itsoptical properties.

FIG. 9 includes (a) through (g) optical characteristics diagrams of theliquid crystal cell 11, the polarizing plates 12 and 13, the A-plate 39,and the C-plates 40, 15, and 16, respectively. Specifically, FIG. 9( b)shows an optical axis 39 a of the A-plate 39, and FIG. 9( c) shows anoptical axis 40 a of the C-plate 40 (note that the optical axis is inthe normal direction with respect to the surface).

A description will now be given of a fourth exemplary embodiment. FIG.10 shows a cross-sectional view of a display unit of the fourthexemplary embodiment.

In the fourth exemplary embodiment the C-plates 15 and 16 of the thirdexemplary embodiment are replaced with an optical plate 38 which isdescribed above in connection with the second exemplary embodiment. Thisconfiguration can provide the same or substantially same effects as thatof the third exemplary embodiment in terms of its optical properties.

FIG. 11 includes (a) through (f) optical characteristics diagrams of theliquid crystal cell 11, the polarizing plates 12 and 13, the opticalplate 38, the A-plate 39, and the C-plates 40, respectively.

FIG. 12 shows a cross-sectional view of a display unit of a referenceexample. This reference example is made in accordance with the techniqueof the publication of Japanese Patent No. 3330574, and uses only biaxialplates as viewing angle compensation means.

It should be noted that because there is a limit to increasing theretardation value in the thickness direction through stretching anorbornene-based resin material, this reference configuration uses threebiaxial plates 41, 42, and 43.

As shown in FIG. 12, the biaxial plate 41 is disposed between the liquidcrystal cell 11 having a retardation of 800 nm and the front sidepolarizing plate 12.

This biaxial plate 41 is configured to have a retardation in thein-plane direction of 50 nm and a retardation in the thickness directionof 200 nm, and is disposed such that the delay phase axis thereof in thein-plane direction is perpendicular to the absorption axis of the frontside polarizing plate 12.

In addition to this, two biaxial plates 42 and 43 are disposed betweenthe liquid crystal cell 11 and the rear side polarizing plate 13. Thebiaxial plates 42 and 43 each have a retardation in the in-planedirection of 25 nm and a retardation in the thickness direction of 200nm. Furthermore, the biaxial plates 42 and 43 are configured to haverespective delay phase axes in the in-plane direction so that they areparallel to each other and are perpendicular to the absorption axis ofthe adjacent rear side polarizing plate 13.

FIG. 13 includes (a) through (f) optical characteristics diagrams of theliquid crystal cell 11, the polarizing plates 12 and 13, and the biaxialplates 41, 42, and 43, respectively. Specifically, FIGS. 13( b), 13(d)and 13(e) show delay phase axes 41 a, 42 a, and 43 a of the respectivebiaxial plates 41, 42, and 43, respectively.

A description will now be given of the effects of the presentlydisclosed subject matter. FIG. 14 is a graph showing the viewing anglecharacteristics of liquid crystal displays made in accordance with theprinciples of the presently disclosed subject matter and a liquidcrystal display made in accordance with the reference techniquedescribed above. This graph shows the change in transmittance when novoltage is applied to the liquid crystal display (normally blackdisplay) when the viewing angle is changed towards −90 degrees and +90degrees in the left and right directions of the liquid crystal displaywith respect to zero (0) degree, which is the direction towards whichthe liquid crystal molecules are oriented during the application ofvoltage (in other words, when the normal direction is defined as12-o'clock direction in a clock, the viewing angle is changed towards9-o'clock direction and 3-o'clock direction).

In this graph, the curve A represents the viewing angle characteristicsof the liquid crystal display of the first exemplary embodiment (shownin FIGS. 4 and 5) and the curve B represents the viewing anglecharacteristics of the liquid crystal display of the third exemplaryembodiment (shown in FIGS. 8 and 9). The curve C represents the viewingangle characteristics of the liquid crystal display of the referenceexample (shown in FIGS. 12 and 13).

As understood from the curve C of the viewing angle characteristics,even though the retardation values in the in-plane direction and thethickness direction have been optimized, the transmittance increaseswhen the viewing angle is changed to 40 degrees or more in the right andleft directions. Therefore, in this reference example, light passesthrough the liquid crystal display even in a normally black displayarea, which is undesirable. Although the change value in transmittanceis not so large, the change will be reflected on readily recognizablecolor tone changes in actual cases. In addition to this, the referenceexample shows the asymmetric viewing angle characteristics as can beseen from the diagram. In particular, when the viewing angle is changedtowards −90 degrees (towards 9-o'clock direction), a significant changein transmittance occurred.

In contrast, the liquid crystal displays made in accordance with theprinciples of the presently disclosed subject matter can show a lowtransmittance even at the deeper viewing angles with excellent symmetryas can be seen from the curves A and B.

As described above, various exemplary embodiments of the disclosedsubject matter have been described. In these exemplary embodiments, theretardation values of the respective compensation plates are configuredto provide excellent viewing angle characteristics when using a verticalalignment type liquid crystal cell having a retardation of about 600 nmor more.

In the described exemplary embodiments, monodomain LCDs using rubbingtechnique are exemplified. The disclosed subject matter is not limitedthereto, and is applicable to multidomain LCDs because the presentlydisclosed subject matter relates to an optical characteristic when novoltage is applied.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A liquid crystal display, comprising: a vertical alignment typeliquid crystal cell having a liquid crystal layer containing liquidcrystal molecules, a retardation of the liquid crystal layer beingconfigured to be about 600 nm or more; a first polarizing plate and asecond polarizing plate provided to respective sides of the liquidcrystal cell, the first and second polarizing plates each having anabsorption axis and being cross-Nicol disposed, the first and secondpolarizing plates being disposed such that the respective absorptionaxes form an angle of 45 degrees ±several degrees with respect to adirection in which the liquid crystal molecules are slanted byapplication of a voltage greater than a threshold voltage; a biaxialplate provided between the liquid crystal cell and the first polarizingplate, the biaxial plate being directly optically coupled to the liquidcrystal cell and the first polarizing plate, respectively, the biaxialplate having refractive indices nx, ny, and nz in in-plane directionsand in a thickness direction, respectively, in which a relationship ofnx>ny>nz is satisfied, the biaxial plate being disposed such that itsdelay phase axis in the in-plane direction is substantiallyperpendicular to the absorption axis of the first polarizing plate; anda C-plate provided between the liquid crystal cell and the secondpolarizing plate, the C-plate being directly optically coupled to theliquid crystal cell and the second polarizing plate, respectively, theC-plate having refractive indices nx, ny, and nz in in-plane directionsand in a thickness direction, respectively, in which a relationship ofnx=ny>nz is satisfied.
 2. The liquid crystal display according to claim1, wherein the biaxial plate has a retardation in the in-plane directionof about 100 nm or less.
 3. The liquid crystal display according toclaim 1, wherein the C-plate disposed between the liquid crystal celland the second polarizing plate is formed of two or more stackedC-plates.
 4. The liquid crystal display according to claim 2, whereinthe C-plate disposed between the liquid crystal cell and the secondpolarizing plate is formed of two or more stacked C-plates.
 5. Theliquid crystal display according to claim 1, wherein the C-platedisposed between the liquid crystal cell and the second polarizing plateis formed of a cholesteric liquid crystal polymer.